def get():
    return list(map(int, input().strip().split(' ')))

N, K = get()

count = 0

def counting(n, k):
    count = 0
    s = [k + 1]
    while len(s) > 0:
        x = s.pop()
        if x <= n:
            count += 1
            s.append(x + 1)
            s.append(x + 1)
    return count

count = counting(N, K)
if K == 1:
    count -= 1
print(count)